use [] and not undefined for missing vclock in search_with_vclock
use [] and not undefined for missing vclock in search_with_vclock

Because [] is valid vclock and undefined is not. Particularly, we can
pass [] to vclock:count_changes

Change-Id: I35cdc01096dd96b6559f780dc0a9f6f0a4a8006f
Reviewed-on: http://review.couchbase.org/44451
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

nimishzynga/ns_server,ceejatec/ns_server,membase/ns_server,nimishzynga/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,nimishzynga/ns_server,membase/ns_server,ceejatec/ns_server,mschoch/ns_server,nimishzynga/ns_server,mschoch/ns_server,mschoch/ns_server,membase/ns_server,nimishzynga/ns_server,membase/ns_server,mschoch/ns_server,ceejatec/ns_server,membase/ns_server,nimishzynga/ns_server,mschoch/ns_server,mschoch/ns_server,ceejatec/ns_server